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+[[!meta copyright="Copyright © 2011 Free Software Foundation, Inc."]]
+
+[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
+id="license" text="Permission is granted to copy, distribute and/or modify this
+document under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no Invariant
+Sections, no Front-Cover Texts, and no Back-Cover Texts.  A copy of the license
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
+
+[[!tag open_issue_glibc]]
+
+IRC, freenode, #hurd, 2011-07-22
+
+    [additional init-first.c patch]
+    < tschwinge> civodul: The only thing I wonder about: Roland also once had
+      done similar changes, which I then found they didn'T work with GCC 4.1,
+      and backed them out in 08f53ee9d265ffdc7e0affd6acf346cceeb65559 and fixed
+      the issue differently in d8d27e633a7860b37fd2e3142822b640a066cc0f (and
+      e17cef66140d4c97710ea88bd8d12612799e1e0f).  Have you reviewed this?
+    < tschwinge> That's in the Savannah glibc repository.
+    < tschwinge> And this has been in 2007, four years ago.  I don't remember
+      all the details.
+    < tschwinge> And here is quite a good summary of this stuff, from
+      init-first.c:
+    < tschwinge> /* XXX This is all a crock and I am not happy with it.
+    < tschwinge>    This poorly-named function is called by static-start.S,
+    < civodul> braunr: thanks; i must admit it took me a while to figure it out
+      ;-)
+    < tschwinge>    which should not exist at all.  */
+    < tschwinge> civodul: I can imagine...  :-/
+    < civodul> tschwinge: re Roland's changes, that's weird; i plan to try to
+      reinstate his change and see if it works
+    < civodul> now, i won't test with GCC 4.1...
+    < tschwinge> Yeah...
+    < tschwinge> I'm happy if it works with 4.4 onwards.
+    < tschwinge> civodul: And it's safe (in GCC terms) to write to ``* ((void
+      **) __builtin_frame_address (0) + 1)'', and similar?
+    < tschwinge> Or should we be coding this few stuff in assembly?
+    < civodul> tschwinge: well, we should add a compile-time assertion for
+      __builtin_return_address (0) == *((void**)__builtin_frame_address (0) +
+      1)
+    < civodul> (i think GCC can figure it out at compile-time)
+    < civodul> but on IA32 it should always be true
+    < civodul> what's the name of glibc's compile-time assert macro already?
+    < tschwinge> I wonder whether that might interfere with some of GCC's
+      optimizations?
+    < civodul> what?
+    < tschwinge> Well, it seems unclean for me to be modifying a function's
+      return address from within C code.
+    < tschwinge> civodul: I added a verify.h in the t/verify.h branch.  But
+      people didn't really like it too much.  They rather wanted to directly
+      inline the array[(cond)?1:-1] code.
+    < civodul> ok
+    < civodul> i remember a debate about Gnulib's verify.h
+    < civodul> i thought something comparable had landed eventually
+    < tschwinge> civodul: Oh, maybe I missed it.
+    < tschwinge> civodul: In init-first.c:init, what about the usage of
+      data[-1] in the else path (not using cthreads) -- is that good as-is?
+    < civodul> tschwinge: oooh, it probably needs to fixed too
+    < civodul> but i haven't reached that point yet ;-)
+     * civodul tries to cross-bootstrap GNU from scratch
+    < tschwinge> civodul: I'd be happy to learn what was wrong with Roland's
+      original idea of fixing this.  Or perhaps this was a GCC 4.1 bug?  Or
+      perhaps GCC was inlining to much, and then got confused with frames and
+      return addresses?
+    < civodul> tschwinge: Roland's change looks good to me, so it could have
+      been a GCC bug
+    < civodul> tschwinge: OK to commit the patch to t/init-first.c (with both
+      data[-1] replaced)?
+    < tschwinge> civodul: OK, if you are confident that it works with GCC 4.4
+      onwards.  If yes, please add your changelog snippet to .topmsg, and also
+      add a not that Roland's original code may in fact have been fine, and we
+      may have hit a compiler bug.
+    < civodul> tschwinge: OK, will do
+    < civodul> tschwinge: though regarding Roland's change, i'd prefer to
+      actually test and see
+    < tschwinge> civodul: Thanks!